THE GALLATIN MOUNTAINS. 31 



QUADRANT MOUNTAIN, BANNOCK PEAK, AND THE VALLEY OF THE 



GALLATIN RIVER. 



In the less disturbed eastern portion of the Gallatin Range the Cam- 

 brian and Devonian strata pass northward with a low northeasterly dip, dis- 

 appearing beneath the more massive beds of Carboniferous limestone along 

 the base of the mountains north of Panther Creek. The bold southern 

 escarpments of Quadrant Mountain and Bannock Peak exhibit almost the 

 entire section of Carboniferous strata, since they are topped near the summit 

 of the former mountain by Juratrias beds. The nearly horizontal beds form 

 massive cliffs that extend with gentle inclination along the eastern escarp- 

 ment of this mountain, in lines parallel to the slope of its plateau-like top, 

 and that sink beneath the level of the valley as Fawn Creek is approached. 

 They may be plainly made out in Mr. Holmes's panoramic sketch of the 

 Gallatin Range, PI. IV. Their character in Bannock Peak is seen in PI. VIII. 

 From here they extend westward along both sides and the bottom of the 

 valley of the Gallatin River, forming the cliff along its northern side and 

 dipping at a low angle toward the southeast, while on the south they form 

 a high ridge and the mountainous spur of Crowfoot Ridge. 



BANNOCK PEAK. 



Bannock Peak is a sharp mountain summit north of the head of Panther 

 Creek. Resting upon the more readily eroded beds of the Silurian and 

 Devonian terranes, the massive Madison limestones form the main mass of 

 the mountain and are capped by the resistant beds of the Quadrant quartzite, 

 whose white ledges form a bold escarpment that encircles the peak. 



On the northern side of the mountain a section was made of the strata 

 exposed in the wall of the amphitheater cut between this peak and the broad 

 plateau summit of Quadrant Mountain. This amphitheater, though appar- 

 ently open, as shown on the map, is divided by a spur projecting southward 

 from the extreme western end of Quadrant Mountain. This section was 

 made from the bed of Panther Creek up the center of the amphitheater to 

 the crest of the ridge dividing' this from the amphitheater at the head of 

 Fawn Creek. The beds are exposed in a series of steps or benches, the 

 lowest strata being the arenaceous Jefferson limestones, the underlying beds 

 being covered by drift. 



The beds dip N. 21° W. at 8°, the determination being made on No. 4 

 of the section 



